1. Field of the Invention
The present invention relates to a paper pickup device and an image forming apparatus having the same. More particularly, the present invention relates to a paper pickup device which relatively easily replaces a pickup roller to prevent the pickup roller from vibrating.
2. Description of the Related Art
In general, an image forming apparatus such as a laser beam printer, an LED printer, a digital copying machine or a facsimile forms an electrostatic latent image by radiating light on a photosensitive body charged to a uniform potential. The image forming apparatus develops the electrostatic latent image by supplying a developing agent to the electrostatic latent image using a developing unit and transfers the developed image onto an intermediate transfer belt or a sheet of paper. Then, the image forming apparatus fuses the image onto the sheet of paper. Consequently, a monochrome image or a color image is formed on the sheet of paper.
Sheets of paper are stacked on a paper feeding cassette of an image forming apparatus. Each sheet of paper is picked up by a pickup roller one by one and fed along a predetermined feeding path so that an image may be formed.
FIG. 1 is a perspective view of a conventional paper pickup device. FIGS. 2 and 3 are perspective views illustrating an operation of separating a driven shaft from a driving shaft so as to replace a pickup roller.
Referring to FIGS. 1-3, a paper pickup device 20 includes a frame 10, a driving shaft 23, and a driven shaft 27. The driving shaft 23 transfers a rotating force to the driven shaft 27 and includes a rotating portion 22 to which a driving force is transferred. The driving shaft 23 further includes a sleeve 24 and a spring 25. The sleeve 24 slides along a lengthwise direction of the driving shaft 23. A groove 24a, to which the driven shaft 27 is coupled, is formed on one side of the sleeve 24. The spring 25 surrounds the driving shaft 23 in a lengthwise direction and elastically biases the other side of the sleeve 24 toward the driven shaft 27. The driving shaft 23 is rotatably supported by the frame 10.
The driven shaft 27 includes a rib 27a that will be coupled to the groove 24a. A pickup roller 28 is installed on the driven shaft 27. A rotating force of the driving shaft 23 is transferred to the driven shaft 27 by the rib 27a inserted into the groove 24a. When the driven shaft 27 is rotated, the rotating force is transferred to the pickup roller 28. In this case, the spring 25 elastically biases the sleeve 24 toward the driven shaft 27 so that the groove 24a and the rib 27a are coupled to each other.
The surface of the pickup roller 28 wears after a predetermined number of rotations. Thus, the pickup roller 28 loses the ability to impart a frictional force. Thus the pickup roller 28 should be replaced with another one. In order to replace the pickup roller 28, as shown in FIGS. 2 and 3, the sleeve 24 is slid along the directional arrow toward the rotating portion 22. The groove 24a is spaced apart from the rib 27a by a predetermined gap and then the driven shaft 27 separates from the driving shaft 23.
Therefore, the operation of replacing the driven shaft 27 is relatively complicated. Moreover, there is a distance between the rib 27a and the groove 24a so that the rib 27a can be inserted into the groove 24a. Due to this distance, when the rotating force is transferred to the driven shaft 27 from the driving shaft 23, the driven shaft 27 and the driving shaft 23 vibrates up and down. As such, the pickup roller 28 cannot pick up the sheet of paper smoothly.
Accordingly, there is a need for an image forming apparatus having a paper pickup device which prevents a driving shaft and a driven shaft from vibrating.